1. Field of the Invention
The present invention relates to stabilizers for use in polymeric compositions. More particularly, the present invention relates to blends of phosphite or phosphonite compounds that have improved hydrolytic stability for use in the stabilization of polymeric compositions.
2. Description of Related Art
The need for stabilization of polymeric compositions is known, and the use of compounds such as hydroxylamines, amine oxides, lactones, hindered phenolics, and phosphites is also generally known.
The purpose of stabilizers is to prevent deterioration of polymers during processing at high temperatures and also to permit the manufacture of products with increased intrinsic quality because of the enhancement of their resistance to thermal and light degradation during use. In addition, because of these enhanced properties, their versatility is increased, and wider use is thereby made possible.
It is well known that phosphites are essential components in the stabilization of polymers. There is a synergistic effect between phenols and phosphites during melt processing. Phosphites decompose hydroperoxides while phenols trap peroxy radicals. To maximize this synergy, the phosphites should exhibit acceptable hydrolytic stability and have good storage stability in particular in hot and high humidity environments in order to minimize formation of undesired species that can result in feeding issues, black specks, and the like, thereby resulting in poor performance.
U.S. Pat. No. 5,438,086 discloses a class of hydrolytically stable bis(aralkylphenyl)pentaerythritol diphosphites that are said to be suitable as antioxidant additives in polyolefins, particularly, in polypropylene. The diphosphites are of low volatility, have a high thermal decomposition temperature, and resist yellowing when blended into a polyolefin base. A preferred diphosphite is bis(2,4-dicumylphenyl)pentaerythritol diphosphite.
U.S. Pat. No. 5,856,550 discloses compositions comprising (a) 25 to 99% of organic phosphite or phosphonite, based on the total weight of the composition, (b) an effective stabilizing amount of organic amine, and (c) an effective stabilizing amount of acid-binding metal salt, wherein the composition comprises no organic polymers or alkali metal phosphates as further components, as well as a process for stabilizing organic phosphites or phosphonites against hydrolysis by addition of organic amine and acid-binding metal salt. The compositions are said to be stable to hydrolysis and have good storage stability even at high atmospheric humidity. The compositions and process products can be used as stabilizers for organic material against the harmful action of heat, oxygen and/or light.
U.S. Pat. No. 6,680,351 discloses a polyolefin composition having high resistance to degradation, the composition being formed by combining components comprising at least one polyolefin component produced from a transition metal halide catalyst, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, triisopropanolamine, a hydrotalcite component, and at least one phenol component.
U.S. Pat. No. 7,157,511 discloses that the whiteness and stability after processing of a polyolefin have been found to be improved upon the addition of a combination of at least one high activity phosphite and at least one hydrolytically stable phosphite.
U.S. Pat. No. 7,176,252 discloses a solid phosphite composite, having at least a portion in amorphous form, which includes at least one, preferably two or more phosphite antioxidants or alternatively at least one phosphite and at least one other polymer additive. The phosphites, at least one of which can initially be a liquid, are generally uniformly distributed since they are melt blended. A desired class of phosphites is the bis(arylalkylphenyl)pentaerythritol diphosphites, at least a portion of which is in amorphous form.
U.S. Pat. No. 7,361,703 discloses a process for the stabilization of thermoplastic polyolefins during melt processing operations. The stabilizer package of this invention is phenol free and must contain at least one aryl monophosphite and at least one diphosphite. The process of this invention is said to be suitable for the manufacture of polyethylene film.
U.S. Patent Application Publication No. 2005/0009967 discloses a process for the preparation of a neo diol phosphite stabilizer by a direct/solvent-less method, wherein a neoalkyl chlorophosphite is reacted directly with a mono- or di-substituted hydroxylated aromatic compound, for neo diol phosphite product having little or no odor. Also provided are polymeric compositions comprising a stabilizing amount of a neo diol phosphite having low to no odor.
U.S. Patent Application Publication No. 2007/0105992 discloses a stabilized composition comprising:
(A) a polymeric resin, and
(B) a stabilizing amount of a phosphite of the structure
wherein
R1, R2, R3, and R4 are independently selected from the group consisting of alkyl moieties and substituted cycloalkyl moieties of the structure
wherein
R14, R15, R16, R17, and R18 are independently selected from the group consisting of hydrogen and hydrocarbyl, provided that at least one of R14, R15, R16, R17, and R18 is not hydrogen and that no more than one of R1, R2, and R3 is alkyl,
R9 and R10 are independently selected from the group consisting of hydrogen and hydrocarbyl, and
Ar is an aromatic moiety.
The disclosures of the foregoing are incorporated herein by reference in their entirety.